The purpose of the Toxicokinetic Susceptibility Research Core (TSRC) is to foster collaboration and sharing of ideas, data and methods among the members in a manner that enhances existing Center projects and motivates proposals for future studies. The specific objectives of the TSRC are to: 1) Support and expand collaborative research involving the following loci: i) biomarkers of exposure and effect, ii) biologically-based modeling, and iii) hepatotoxicity, as well as research involving two or more of these areas. 2) Establish effective mechanisms for sharing ideas within and among focus groups and expanding Core membership to other relevant scientists. 3) Increase interactions with other Research and Facility Cores to foster application of sound toxicokinetic principles in study designs of Center members and affiliates.